1. Field of the Invention
The present invention relates to hard films. More specifically, it relates to hard films to be arranged on cutting tools such as tips, drills, and end mills, and tools such as forging dies and stamping punches.
2. Description of the Related Art
For improving wear resistance of cutting tools, hard films such as TiN, TiCN, or TiAlN are applied to base materials such as high-speed tool steel, cemented carbide, or cermet. In particular, multicomponent (carbo) nitride films of titanium and aluminum such as TiAlN films and TiAlCN films (hereinafter referred to as “TiAl hard films”), as disclosed in Japanese Patent No. 2644710, exhibit excellent wear resistance, and they are suitably applied to cutting tools for high-speed cutting operation or for cutting materials with high hardness such as hardened steels. However, further demands have been made to provide hard films with more excellent wear resistance with increasing hardness of materials to be cut or increasing speed of cutting operation. In addition, high-speed tool steels such as Japanese Industrial Standards (JIS) SKD11 steel are often cut by using cutting tools at high speed instead of electrodischarge machining. Therefore, hard films excellent not only in wear resistance but also in oxidation resistance are required.
Another possible solution is a technique of adding Cr or V to TiAl hard films to thereby maintain a high-hardness cubic crystal structure while increasing the Al content to thereby yield films with improved oxidation resistance (Japanese Laid-open (Unexamined) Patent Publications (JP-A) No. 2003-71610 and No. 2003-34858). CrAlVN films containing no Ti have also been proposed.